Future studies: Studies on N-propylnorapomorphine (NPA) to ensure its introduction as an adjunct drug in the treatment of Parkinsonism. The efficacy of levodopa therapy, its side effects and progression of disease, in the original patient population as a function of time on treatment will be further analyzed. Study further why some patients maintain the original therapeutic benefits and other do not. Effects of Choline-Cl on the levodopa-induced side effects, including psychosis and dementia. Immune responses of animals chronically tested with levodopa, untreated and levodopa-treated patients to ascertain whether this drug alters these responses and whether it is capable of reversing age-associated immune dysfunction. Studies on whether managanese body burdens are altered in patients with levodopa-induced side effects and seizure disorders. The relationship of levodopa's cerebral effects in animals to the brain DA-sensitive adenylate cyclase and elucidation of the mechanism involved on the effect of somatostatin and endorphine on levodopa metabolism in animals. The effects of levodopa administered for life on enzymes involved in catecholamine metabolism, brain melanin and life expectancy. Testing the effectiveness of the prototype DA-receptor agonisn, N-n-propyl-N-n-butyl dopamine analog in Parkinsonism. The structure-activity relationships of the new N,N-disubstituted Da analogs after systematic and intracerebral administration in intact animals and models. Evaluation of DA-receptor antagonists on apomorphine- and levodopa-induced behavioral effects in rodents. The synthesis and testing of peptides with levodopa as an A-terminal and D-alanine as a C-terminal amino acid for possible dopamimetic and/or neurotransmitter modulating effects. Development of analytical methods for the determination of various DA analogs. Continue the collaborative efforts for the synthesis and testing of N-n-disubstituted DA analogs for CNS and cardiovascular dopamimetic effects.